The present invention relates generally to agricultural implements, and more particularly to an automatic guidance system for row crop cultivators and similar implements.
When cultivating crops, it is very important that the tillage implement be carefully positioned with respect to the rows of plants to avoid crop loss. As the trend towards larger farm implements continues, the importance of proper guidance in the field is magnified since an error in positioning can destroy plants in numerous rows. Operator fatigue and reduced operator concentration, even for very short periods of time, can result in improper guidance with significant crop loss.
Various systems are available for automatic guidance but none have been entirely satisfactory. Some types, such as shown in U.S. Pat. No. 4,161,143, control the steering on the tractor, but these require additions or modifications to the tractor steering mechanism and do not provide quick, positive alignment of a rear-mounted implement with the crop rows, which is necessary to avoid plant damage.
Other types of guidance systems, such as exemplified in U.S. Pat. Nos. 4,184,551 and 4,228,860, utilize steerable rear coulters and have been found to do a satisfactory job of automatically positioning an implement in most conditions. However, the coulters and the framework required to mount the coulters on the implement are relatively heavy and therefore lift assist wheels must be added which increase the cost of the implement. With coulter guidance, the three-point hitch mounting the implement to the tractor is permitted to sway so that the coulters can move the implement transversely. Sway can be detrimental on slopes and hillsides, particularly when the implement is being lowered into the field-working position. As the three-point hitch drops below contact with sway blocks, which normally restrain side motion, the implement will fall down-slope until the coulters can act to properly align the implement with the rows. Often some plants are damaged or destroyed before the guidance system can adjust the implement. The steerable coulter systems, as well as other types of prior art systems, have lacked adequate controls to manually adjust the position of the implement with respect to the tractor or to lock the implement in a given lateral position with respect to the tractor.
Other types of systems for guiding implements have utilized toolbars connected to the tractor hitch structure with sliding or rolling members so that the toolbar can be shifted laterally to position the tools with respect to the rows of crops. Such a system is shown, for example, in U.S. Pat. No. 3,208,535. Although such a system can usually provide quick, positive toolbar shifting, the sliding or rolling members are subjected to heavy loading under adverse environmental conditions. Friction and wear result in a relatively short life expectancy of the sliding or rolling members, and binding can occur.
Another type of guidance system, exemplified in U.S. Pat. No. 4,180,133, utilizes a hydraulically controlled swinging drawbar hitch. Although adequate for towed implements, such a system is not adaptable for tractor-mounted implements such as row crop cultivators.
It is therefore an object of the present invention to provide an improved guidance system for use with agricultural implements. It is another object to provide such a system for a tractor-mounted implement.
It is a further object of the invention to provide an improved guidance system for an agricultural implement which overcomes the aforementioned problems of previously available systems.
It is another object of the present invention to provide a row guidance system for an implement which is lighter and more compact than at least some of the prior art systems, and which does not significantly increase the distance between the rear extremity of the implement and the rear of the tractor or towing vehicle.
It is yet another object to provide an improved guidance system for an implement which provides more positive and accurate control of the implement during end turns, particularly on sloping ground.
It is yet a further object of the present invention to provide an implement guidance system with enhanced automatic control for centering both the implement and furrow sensor when the implement is raised out of the ground. It is another object to provide such a system with improved control features for manually adjusting and fixing the transverse position of the implement with respect to the tractor, even on sloping ground.
It is still another object of the invention to provide an improved linkage for an implement guidance system for transversely positioning a toolbar with respect to the tractor hitch. It is another object to provide such a linkage which is reliable and compact and which does not significantly increase the weight of the implement or the distance that the implement projects rearwardly behind the tractor. It is a further object to provide a self-centering hydraulic cylinder arrangement for such a device.
In accordance with the above objects, a toolbar of a row crop cultivator or the like is connected to a tractor by a relatively compact parallel linkage hitch, which replaces the standard three-point hitch of the implement, to permit lateral movement in either direction from center. The parallel linkage hitch maintains the toolbar perpendicular to the forward direction and permits the sway blocks or other stabilizing means on the tractor three-point to be engaged during operation in the field for stability on slopes. A preestablished furrow or mark placed in the ground at planting is sensed by two independent furrow followers mounted on the toolbar one behind the other. The followers are mounted on trailing arms which pivot both vertically and laterally. Associated with each follower is a pair of switches, one on each side of the arm, activated by lateral movement of the follower. The switches on each side are connected in series. Lateral movement of the cultivator with respect to the furrow (and therefore the crop row) activates one set of series-connected switches which, in turn, operates a hydraulic positioning cylinder. The cylinder moves the toolbar to center the arms with respect to the switches and thereby position the cultivator with respect to the rows. The series-connected switches require both followers to indicate the same directional error to eliminate erratic signals caused by a follower bouncing over clods or other obstacles.
A V-shaped stop under each of the sensor arms automatically positions the followers at the null points when the implement is lifted from the ground. Two switches on the hydraulic positioning cylinder are energized as the implement is raised to automatically center the implement in preparation for alignment with the next rows to be cultivated. A jog or manual overrider switch is located in the tractor cab so the operator can move the implement transversely to override automatic steering when the implement is not lined up properly with the rows. The implement may be positively steered uphill and held in position when necessary for proper alignment on slopes.
These and other objects, features and advantages of the present invention will become apparent to those skilled in the art from the description which follows when taken with the accompanying drawings.